Evaluate f(x)=−x−7 when x=−2 0 and 5

Julius went on a volunteer trip to centralamerica and took medical supplies with him.he packed a bag with 50 pounds of supplies.he brought pieces of equipment that weighed10 pounds each and bottles of medicine thatweighed pound each prepresents thenumber of pieces of equipment he broughtand b represents the number of bottles ofmedicine he brought then the total weight canbe represented by the equation 10p+b 50.the brought 3 pieces of equipment, how manybottles of medicine did he bring?